1. Field of the Invention
This invention relates generally to the field of mounting clip assemblies for miniature electronic devices such as paging receivers. More particularly, this invention relates to the field of belt clip assemblies having a controlled manner of failure which results in major damage being confined to at most an inexpensive, sacrificial bracket. This controlled failure mode prevents damage to more expensive components and allows for inexpensive repair.
2. Background of the Invention
Belt clips or mounting clips of various configurations have been used for a number of years in portable electronic devices such as paging receivers. One of the most popular types is a spring loaded belt clip which serves as an attaching mechanism which allows the user to rapidly and securely attach the pager or other electronic device to the user's belt, pocket, or purse to make the device conveniently accessible yet securely mounted.
An exemplary prior art belt clip is used in the MOTOROLA PAGEBOY II.TM. pager which is shown in FIG. 1 in exploded view. This pager includes a plastic housing frame 10, which serves as the primary housing for the internal electronic circuitry. A substantially U-shaped housing cover 15 is made of metal and slides into slots 20 in housing frame 10. An opening 25 at the top of the housing cover 15 allows access to controls which are mounted on housing frame 10. It is interesting to note that housing cover 15 is utilized as the paging receiver's antenna in the MOTOROLA PAGEBOY pager II.TM.. This feature is described in U.S. Pat. No. 3,736,591 to Rennels, et al, the contents of which are hereby incorporated by reference.
On the rear surface of housing cover 15 a pair of tabs 30 are punched from holes 35 and bent outwardly at a right angle to the rear surface of housing cover 15. Each of these tabs 30 additionally have a circular hole 40 punched through them. The center of circular holes 40 lie along a substantially coaxial line.
A lanyard bracket 45 which is somewhat U-shaped also has a circular hole 50 on each side which is made to align with circular holes 40 when lanyard bracket 45 is inserted through holes 35 from the inside of housing cover 15. On one end of lanyard bracket 45 is a lanyard mount 55 including a hole for attaching a lanyard when the user prefers to suspend the pager from a lanyard rather than attach it to his belt.
A belt clip 60 including a passage 65 running through it is attached to the housing member 15 by means of a roll pin 70. A coil spring 75 is utilized to keep belt clip 60 in position so that the lower portion of clip 60 presses against housing member 15 thereby entrapping the user's belt.
When assembled, the roll pin passes through circular hole 40 to circular hole 50 into one side of passage 65 through the coil spring 75 and out the other end of passage 65 to the other circular hole 50 and the other circular hole 40. Support for the belt clip 60 and lanyard bracket 45 is provided by tabs 30 and roll pin 70. In order to open the belt clip, the user has simply to pull on the bottom of the belt clip away from housing cover 15 or push on the top of belt clip 60 toward the housing cover 15. The spring action of coil spring 75 urges the clip closed when pressure is released.
Although this clip arrangement functions well in normal use, when excess force is exerted on belt clip 60 in a direction which forces opening of the clip, the clip itself which is made AISI/ASTM designation 2024 Aluminum generally tends to break at point 80 severing the main body of the belt clip from the pager. This failure mode has been demonstrated to occur when approximately 23 to 30 pounds of opening force is exerted on a lower portion 85 of the belt clip.
Although this breaking force is reasonably high it is readily achieved, for example, when one inadvertently catches the pager on the arm of a chair, etc. while sitting down. Additionally, it is frequently the case that housing cover 15 is deformed in the process of breakage. Although it may be possible to straighten housing cover 15 somewhat and reuse it, since housing cover 15 forms the radio receiver's antenna, the antenna's reception pattern or other characteristics may be disturbed. It is frequently the case that when such an accident occurs, housing cover 15, roll pin 70, lanyard bracket 45, and belt clip 60 must all be replaced at substantial cost to the owner.